Blowers only luke warm

[TROOPER88]

Hi
I have recently taken the engine and gearbox out of my MK3 Golf GTi 8v for the box to be repaired. I also did the belts and clutch.

All is good and the car drives well.

Since it has been back on the road I have noticed that the blowers do not blow out hot air like they used to. It gets luke warm but not much more.

I replaced the water pump and the thermostat when I had the engine out.

The temp gauge is perfect and sits in the middle where it should be at all times.

Any ideas what it could be??
Could there be an air lock somehwhere which is not moving? I have driven a good few hundred miles since I did the work.

Many thanks

[Nick1point9]

Probably an air lock in the heater matrix circuit.

[TROOPER88]

Nick1point9 said:

Probably an air lock in the heater matrix circuit.

Thanks


Run it up to temp with expansion cap off with blowers on hot and full?

[Marf]

TROOPER88 said:

Nick1point9 said:

Probably an air lock in the heater matrix circuit.

Thanks


Run it up to temp with expansion cap off with blowers on hot and full?

Yep, and give it a good sustained revving with the coolant cap off to get the air circulating round the system.

Expect to lose some coolant during the process, i.e. have some more on hand to top up.

Are there any bleed points around the heater matrix?

Edited by Marf on Wednesday 2nd January 14:45

[davepoth]

The other thing to do is to do all of the above on a steep slope so that the expansion tank is much higher than the heater matrix, which should encourage the bubbles out.

[TROOPER88]

Hi Guys
Have tried all of the above but unfortunately the problem remains.

Tried twice (once with the front end raised) to run the car with the cap off. Tried massaging the pipes etc, all the time with the blowers on full but blowers still only warm, not hot.

I am guessing it can only be the thermostat at fault?

How can it be faulty, not opening fully?

Thanks

[davepoth]

TROOPER88 said:

Hi Guys
Have tried all of the above but unfortunately the problem remains.

Tried twice (once with the front end raised) to run the car with the cap off. Tried massaging the pipes etc, all the time with the blowers on full but blowers still only warm, not hot.

I am guessing it can only be the thermostat at fault?

How can it be faulty, not opening fully?

Thanks

Usually opening fully too early would cause the symptom you have, and that's quite often how they fail. Not an expensive thing to change I guess, so probably worth a go. Shouldn't be the cause of your running issue though - if a MK3 has an OBD2 port it's probably worth plugging in to see what the coolant temperature sensors are saying.

[TROOPER88]

davepoth said:

Usually opening fully too early would cause the symptom you have, and that's quite often how they fail. Not an expensive thing to change I guess, so probably worth a go. Shouldn't be the cause of your running issue though - if a MK3 has an OBD2 port it's probably worth plugging in to see what the coolant temperature sensors are saying.

Thanks mate for taking the time to reply.

Would/could a coolant temp sensor cause this?

Cheers

[powerstroke]

TROOPER88 said:

Thanks mate for taking the time to reply.

Would/could a coolant temp sensor cause this?

Cheers

the only thing that would stop the engine getting to working temp would be the thermostat does the temp gauge go down when you drive ?? if so that would surgest the stat is stuck open ,or maybe the heater matrix is blocked or the heater control flap is stuck ... I think you need to work out if the engine is warming up then check both pipes to and from the heater are hot then check if the heater flaps are moving, cable ajustment or stepper motor if you have climate control

[Steve_D]

Can you get at the heater pipes? If so then disconnect and run fresh water through the heater using a garden hose. Do it in both directions to flush out any crud.
Finally reconnect to the car without letting the water drain from the heater.

Steve

[davepoth]

TROOPER88 said:

Thanks mate for taking the time to reply.

Would/could a coolant temp sensor cause this?

Cheers

Probably wouldn't be the cause - the temperature sensor usually only controls cold start enrichment (the "choke").

Usually the temperature gauge on a car is very inaccurate - the middle being OK, the red bit "Not OK", so if you want an accurate reading it's best to read the sensor directly and figure out whether the car is getting hot enough to open a properly working thermostat (in which case it's not the problem) or if the stat is opening too early (in which case it is). If you've not got the kit to do it, it'd be cheaper to put a new thermostat on, so I'd probably do that first to see if it helps.

[TROOPER88]

Hi Guys

Well the thermostat is not the problem.
It is a time consuming job changing the stat on a mk3 Golf GTi. You have to remove the drive belt and remove the power steering pump bracket out of the way just to be able to see the housing. 2 hours wasted.

The facts:

Was running perfectly before I removed the engine.

Has a new water pump

Have run the car up to temp with cap of expansion tank a few times to try and remove any air.

The temp needle sits perfectly in the middle.

Before I removed the engine, even on the coldest of days the Golf would be warm as toast withing 2 miles max.

The ONLY thing this could be is air as nothing else has changed?

When I squeeze the two rubber sections of hose going to and from the bulk head to the matrix, it feels to me like there is little or no water flowing. They are soft and although hot to touch (when up to temp can only keep them squezzed for a few secs as so hot) they do not get firm.

I plugged a basic code reader in and there are no faults.

I am stuck!!

In the morn I will do as was suggested above and try and remove the bulk head hoses and run water through the.

Help, lol!

[annodomini2]

What if you pull it to cold, actuator connected up the wrong way around?

[TROOPER88]

annodomini2 said:

What if you pull it to cold, actuator connected up the wrong way around?

If you turn the dial to cold the temp does get colder.

When on hot (max) it gets to barely luke warm.

Thanks

[TROOPER88]

Just had a look at the 2 hoses where they connect to the slam panel. There was a material pipe that was not connected to a white short stud coming from the mounting for the two hoses.

I pushed it back on but not sure what it does? I tried pushing the white stud incase it was a bleed nipple but there is no movement in it.

I am guessing the pipe is some kind of vacuum. Even with it connected the problem still remains...

[annodomini2]

Heater matrix clogged up with crud?

[Steve_D]

annodomini2 said:

Heater matrix clogged up with crud?

I've already suggested back and forward flushing it but I don't think he's done it yet.

Steve

[TROOPER88]

Steve_D said:

I've already suggested back and forward flushing it but I don't think he's done it yet.

Steve

Hi
Going to try this first thing.

How could it be full of crud if it was working 100% before the engine came out?

Cheers and I will report back

[SuperchargedVR6]

Did your Golf ever get the heater matrix bypass fitted under recall? The matrices had a habit of bursting on MK2s/MK3s/Corrados. VW fitted a valve that recirculates coolant away from the matrix in the event of failure.

If you have it, there'll be a metal or plastic valve on one of the matrix hoses.

I'm sure I remember reading somewhere that if the coolant is drained, the valve activates because it thinks the matrix has burst. I could be wrong. Try asking on clubgti.

[TROOPER88]

SuperchargedVR6 said:

Did your Golf ever get the heater matrix bypass fitted under recall? The matrices had a habit of bursting on MK2s/MK3s/Corrados. VW fitted a valve that recirculates coolant away from the matrix in the event of failure.

If you have it, there'll be a metal or plastic valve on one of the matrix hoses.

I'm sure I remember reading somewhere that if the coolant is drained, the valve activates because it thinks the matrix has burst. I could be wrong. Try asking on clubgti.

Hi
Well I just removed both hoses to the matrix at the bulk head and ran the hose through. Clear water flows nicely with no evidence of a blockage.

I will search Goggle for the valve you mention but to be honest dont hold much hope.

Cheers